Now LROC brings you an even more dramatic view of these volcanic domes from an oblique angle (viewing from East to West), from an altitude of 154 km (96 miles) above the lunar surface.

Located along the mare/highlands boundary, on the northeast border of Oceanus Procellarum (36.6°N, 319.9°E), the three Gruithuisen domes Gamma, Delta, and Northwest (NW) are primary examples of lunar silicic volcanism.

A thumbnail image of the 20376 x 6728 oblique NAC montage users can zoom into HERE. The crater Gruithuisen B is 9 km in diameter (north is to the right) [NASA/GSFC/Arizona State University].

Field of view seen at an oblique angle sketched out (arrows) on a photometric work-up of an LROC monochrome Wide Angle Camera (WAC) overview by Maurice Collins, originally presented as a Lunar Picture of the Day (LPOD), September 27, 2010 [NASA/GSFC/Arizona State University].

Silicic volcanism is relatively rare on the Moon. The Gruithuisen Domes pre-date the lunar mare in this region, so some portion of these domes has been covered by mare basalt, although there are also contacts with the older highlands material. Silicic volcanism might have been more widespread during the Moon's early history, however, any evidence for that may be buried beneath the maria. We know that the composition of the Gruithuisen Domes are different from that of the mare and the highlands from Earth-based telescopes, Lunar Prospector gamma-ray spectroscopy data, and Clementine multispectral data. The Gruithuisen Domes are characterized by relatively high reflectance and strong absorptions in the visible and ultraviolet. The Domes are also low in iron and titanium abundance compared to the lunar maria. New data from the Diviner instrument on the LRO spacecraft confirmed that the Gruithuisen Domes are silicic.